Apparatus for reducing contaminants from a chemical mechanical polishing pad

ABSTRACT

The present invention provides an apparatus for reducing contaminants on an unused chemical mechanical polishing pad. The apparatus comprises a rotating vacuum platen for rotating and holding the polishing pad, a traversing arm that moves between a peripheral edge and a center axis of the polishing pad, and a contaminant collection nozzle movably disposed along a length of the traveling arm for collecting contaminants from the polishing pad. Further, the apparatus comprises a vacuum pump for providing a vacuum to the rotating vacuum platen and the contaminant collection nozzle.

BACKGROUND OF THE INVENTION

The present invention relates to polishing pads for chemical mechanical planarization (CMP), and in particular, relates to polishing pads having reduced stress windows formed therein for performing optical end-point detection. Further, the present invention relates to polishing pads having a sealed pressure relief channel to reduce stress on the windows and prevent contamination of the window area.

In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting and dielectric materials are deposited on or removed from a surface of a semiconductor wafer. Thin layers of conducting, semiconducting, and dielectric materials may be deposited by a number of deposition techniques. Common deposition techniques in modern processing include physical vapor deposition (PVD), also known as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and electrochemical plating (ECP).

As layers of materials are sequentially deposited and removed, the uppermost surface of the wafer becomes non-planar. Because subsequent semiconductor processing (e.g., metallization) requires the wafer to have a flat surface, the wafer needs to be planarized. Planarization is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials.

Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique used to planarize substrates, such as semiconductor wafers. In conventional CMP, a wafer carrier is mounted on a carrier assembly and positioned in contact with a polishing pad in a CMP apparatus. The carrier assembly provides a controllable pressure to the wafer, pressing it against the polishing pad. The pad is moved (e.g., rotated) relative to the wafer by an external driving force. Simultaneously therewith, a chemical composition (“slurry”) or other polishing solution is provided between the wafer and the polishing pad. Thus, the wafer surface is thus polished and made planar by the chemical and mechanical action of the pad surface and slurry.

A key component in the polishing performance is the reduction or minimizing of contaminants during the polishing process. Typically, these contaminants are introduced to the process by, for example, by-products from consumed slurries and debris from the pad itself. In an attempt to solve the contamination problem, efforts have been made to flush a polishing pad surface with high pressure deionized water jet to remove particles entrapped in the surface grooves (e.g., U.S. Patent Pub. No. 2002/0090896). Other efforts have been made to manually clean the polishing pad after shutting down the chemical mechanical polishing apparatus by brushing.

Another source of contamination is from the debris introduced to the polishing pad during the manufacture and packaging of the polishing pad, not during the polishing process itself as described above. In other words, contaminants (e.g., dust) can gather on the surface of the polishing pad during, for example, grooving of the pad. Then, this contaminated polishing pad may be packaged and later utilized in a polishing process, potentially effecting the polishing performance.

Unfortunately, although the prior art is replete with methods and apparatuses for reducing contamination issues created during polishing, the art is inadequate in addressing contamination issues created during the manufacturing and packaging of the polishing pad. Although a finished polishing pad is carefully cleaned (typically, using a manual brush) and later packaged in a clean room, there still exists a need for an improved apparatus and method for further cleaning or reducing contamination on an new polishing pad (“unused polishing pad”).

STATEMENT OF THE INVENTION

In one aspect of the invention there is provided an apparatus for reducing contaminants on an unused chemical mechanical polishing pad comprising: a rotating vacuum platen for rotating and holding the polishing pad; a traversing arm that moves between a peripheral edge and a center axis of the polishing pad; a contaminant collection nozzle movably disposed along a length of the traveling arm for collecting dust from the polishing pad; and a vacuum pump for providing a vacuum to the rotating vacuum platen and the dust collector nozzle.

In another aspect of the invention there is provided an apparatus for reducing contaminants on an unused chemical mechanical polishing pad comprising: a rotating vacuum platen for rotating and holding the polishing pad; a traversing arm that moves between a peripheral edge and a center axis of the polishing pad; a contaminant collection nozzle movably disposed along a length of the traveling arm for collecting dust from the polishing pad; and a vacuum pump for providing a vacuum to the rotating vacuum platen and the dust collector nozzle; an enclosure for housing the vacuum platen, traversing arm, contaminant collection nozzle and the vacuum pump.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a frontal view of an apparatus of the present invention for reducing contaminants from a chemical mechanical polishing pad;

FIG. 2 illustrates a cross-sectional view of an apparatus of the present invention for reducing contaminants from a chemical mechanical polishing pad; and

FIG. 3 illustrates an exploded view along line A-A of FIG. 1 of the contaminant collection nozzle and air blast nozzle of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an apparatus for reducing contamination on an unused chemical mechanical polishing pad. In other words, the present invention reduces the contamination on new polishing pads, before it is utilized by the customer in a polishing process. The present apparatus utilizes a unique combination of a traversing arm and nozzles to effectively expel and collect debris or contamination from the surface of the polishing pad.

Referring now to the drawings, FIG. 1 discloses an apparatus 2 comprising a rotating vacuum platen 14 for rotating and holding an unused polishing pad (not shown) to be processed for decontamination. The vacuum platen may hold polishing pads of varying diameters, for example, from 100 mm to 1000 mm. In addition, the platen 14 comprises internal, individual vacuum chambers that may be turned on or off, as desired. In this way, the vacuum is only applied where it is needed (i.e., area taken up by the pad) to hold the polishing pad onto the rotating vacuum platen 14. Apparatus 2 further comprises a traversing arm 18 that travels back and forth between a peripheral edge of the polishing pad to the center axis of the polishing pad, denoted by direction B, for sweeping across the length of the polishing pad. In particular, the traversing arm 18 travels from an edge of the polishing pad to the center of the pad. Note, the traversing arm 18 may move in any direction, as desired. In other words, the traversing arm 18 may move in a semi-circular direction, as denoted by B, or may move across the polishing pad in a straight line, either to the center of the pad or from edge to edge, as desired. Concurrently, as the arm 18 sweeps across the path B, the vacuum platen 14 rotates in a direction C, allowing the contaminant collection nozzle 12 to access the entire surface of the polishing pad. Note, although a single collection nozzle 12 is shown, the invention is not so limited. In particular, the invention may comprise multiple nozzles 12.

Preferably, the vacuum platen 14 may rotate at a speed of between 150 rpm to 850 rpm. More preferably, the vacuum platen 14 may rotate at a speed of between 400 rpm to 800 rpm. Most preferably, the vacuum platen 14 may rotate at a speed of between 700 rpm to 750 rpm.

In addition, the apparatus 2 may optionally comprise an enclosure 16 for housing the vacuum platen 14, traversing arm 18 and contaminant collection nozzle 12. The enclosure 16 may comprise doors 24 that is movably disposed on a side of the enclosure 16. The doors 24 may open to allow easy access to the vacuum platen 14 for attaching a polishing pad to be worked on. Also, the doors may close to prevent, for example, any contaminants that are being expelled from escaping into the processing environment.

Preferably, the collection nozzle 12 is movably disposed on the traversing arm 18. In other words, nozzle 12 travels along the length of the traversing arm 18, in conjunction with the sweeping movement of the traversing arm 18, allowing greater flexibility and coverage of the surface of the polishing pad that is to be cleaned.

Referring now to FIG. 2, a cross-sectional view of the apparatus 2 of the present invention is shown. Here, the contaminant collection nozzle 12 is attached to a traversing arm 18, connected to a traversing arm pivot shaft 20. The pivot shaft 20 allows the traversing arm to sweep across the length of the polishing pad to be worked on. In addition, a vacuum pump 22 is shown connected to the vacuum platen 14 for supplying a vacuum for holding the polishing pad. Also, the vacuum line 28 operates to supply the contaminant collection nozzle 12 with a vacuum from a vacuum source (not shown). Similarly, the air line 26 supplies the nozzle 10 with air from an air source (not shown).

Preferably, the vacuum from the vacuum pump 22 is provided at a pressure of between 0.037 bar (3.7 kPa) to 0.047 bar (4.7 kPa). More preferably, the vacuum is provided at a pressure of between 0.039 bar (3.9 kPa) to 0.046 bar (4.6 kPa). Most preferably, the vacuum is provided at a pressure of between 0.040 bar (4.0 kPa) to 0.045 bar (4.5 kPa).

Referring now to FIG. 3, an exploded view of the contaminant collection nozzle 12 and the traversing arm 18 is shown. In addition, an air blast nozzle 10 is shown for expelling dust, debris and other contaminants from the surface, including grooves, of the polishing pad 4. Hence, the air blast nozzle 10 and the collection nozzle 12 work in conjunction to expel and collect the contaminants. Note, the present invention utilizes air to expel the contaminants from the work surface, rather than liquid (e.g., “high-pressure de-ionized water”) that is widely utilized in the industry during the cleaning of a used polishing pad.

Preferably, the air from the air blast nozzle 10 is directed at the polishing pad 4 at a pressure of between 35 kPa to 620 kPa. More preferably, at a pressure of between 70 kPa to 550 kPa. Most preferably, at a pressure of between 105 kPa to 345 kPa.

Accordingly, the present invention provides an apparatus for reducing contamination on an unused chemical mechanical polishing pad. The present apparatus utilizes a unique combination of a traversing arm and nozzles to effectively expel and collect debris or contamination from the surface of the polishing pad. 

1. A method for expelling and collecting debris from a surface of a chemical mechanical polishing pad, comprising: introducing debris to the surface of the chemical mechanical polishing pad during manufacture; providing an air blast nozzle; providing a contaminant collection nozzle; expelling the debris from the surface of the chemical mechanical polishing pad; wherein the air blast nozzle and the contaminant collection nozzle work in conjunction to expel and collect the debris.
 2. The method of claim 1, wherein the debris are introduced to the polishing pad during manufacture of the polishing pad.
 3. The method of claim 1, wherein the debris are introduced to the polishing pad during grooving of the polishing pad.
 4. The method of claim 1, wherein the air blast nozzle delivers air at a pressure between 35 and 620 kPa.
 5. The method of claim 1, wherein the contaminant collection nozzle collects debris with a vacuum of between 3.7 to 4.7 kPa.
 6. The method of claim 1, further comprising: providing a vacuum platen; holding the chemical mechanical polishing pad on the vacuum platen with vacuum; rotating the vacuum platen and the chemical mechanical polishing pad; and, sweeping the air blast nozzle and contaminant collection nozzle from a center of the chemical mechanical polishing pad to a peripheral edge of the chemical mechanical polishing pad.
 7. The method of claim 6, wherein the debris are introduced to the polishing pad during manufacture of the polishing pad.
 8. The method of claim 6, wherein the debris are introduced to the polishing pad during grooving of the polishing pad.
 9. The method of claim 6, wherein the vacuum platen is rotated at a speed between 150 and 850 rpm.
 10. The method of claim 1, wherein the air blast nozzle delivers air at a pressure between 35 and 620 kPa; and, wherein the contaminant collection nozzle collects debris with a vacuum of between 3.7 to 4.7 kPa. 